AUTOGRAFTING PH-NEGATIVE BLOOD PRECURSOR CELLS IN CHRONIC MYELOID-LEUKEMIA

The study was devised to evaluate whether it was possible to collect P hiladelphia-negative precursor cells in patients with chronic myeloid leukaemia. The approach was based on previous experience showing that complete remission (Ph-negative bone narrow cells) is rarely achieved after chemotherapy and is very short-lasting. We decided to explore wh ether it was possible to collect Ph-negative precursor cells in periph eral blood during the early phase of haemopoietic recovery. These data show that: the collection of Ph-negative precursor cells occurred in 12/16 (75%) patients mobilized within one year of diagnosis (group A) versus 12/33 (36%) in patients with a history of more than one year of disease (group B). Furthermore the numbers of Ph-negative precursor c ells were significantly much higher at diagnosis. Ten patients mobiliz ed at diagnosis were subsequently autografted with such Ph-negative pr ecursor cells. Five of them remain Ph-negative from 4 to 12 months whi le the other five have percentages of Ph-positive cells in their marro w ranging from 20% to 70%. In this stage of the disease the procedure is safe and associated with a very good compliance. Occasional restora tion of Ph-negative haemopoiesis could be observed up to 40 months aft er autograft, in patients of group B, but most of patients revert to P h-positive haemopoiesis. In conclusion these data suggest that it is p ossible to restore Ph-negative haemopoieis in 70% of patients mobilize d at diagnosis. This percentage represent the highest one can obtain w ithout allogeneic BMT, and this includes patients who never would have been cytogenetic responders to IFN-alpha. Whether and how long for Ph -negative status can be maintained is a matter for future observation and study.